00-04 YAMAHA YZ250: Boyesen Rad Valve BOYESEN engineers embarked on a mission to create a new lineage of aerodynamic intake technology by refining the primary performance factors required to increase peak horsepower through design innovation: Aerodynamic Surface Optimization, Model-Specific R Together, these innovations create a new technological benchmark in intake performance. One-piece design. Maintain flow velocity through the valve and redirect intake charge for even distribution to intake ports. Pull a gear higher on uphills; instant acceleration makes passing effortless.